This invention generally relates to well water monitoring equipment and more particularly to a service cable and cable harness for use with submersible pumps and sensors for monitoring the physical properties of well water.
It is not only desirable but in many circumstances legally required to periodically observe and record the physical characteristics of potable water obtained from wells. The properties of interest typically include pressure, temperature, conductivity and PH level. The absolute value and rate of change of these properties can be quite useful in determining water quality and predicting significant changes in quality. Monitoring is normally accomplished with specialized sensors which are lowered into a well and submerged in the water. Typically the sensors will include one or more sensing devices such as a pressure transducer or temperature sensor for detecting the physical properties of interest. The sensors are normally enclosed in a water tight housing and connected to a multi-conductor cable for transmitting power to and signals from the sensor.
In the monitoring process it may also be desirable to periodically obtain a sample of water from a well. Such samples are typically obtained using a submersible sampling pump which is suspended from the end of a service cable and lowered into the well. Typically these pumps are low profile centrifugal design devices which are electrically or pneumatically powered. The service cables provide power and control inputs to the pumps and include a discharge tube through which well water is transported back to the surface. One such cable is described in applicant's U.S. Pat. No. 5,186,253.
One of the problems which designers of submersible sensors and pumps have faced is how to prevent leakage of well water into the sensor or pump housing. The leakage problem is complicated by the fact that in most sensor and pump designs there are a number of possible leakage paths. Typically, the housings for both types of units have hollow cylindrical bodies and at least one end cap removable for servicing purposes. Accordingly, one such leakage path is at the interface between the cylindrical body and the end cap and another is along the interface between the service cable and the end cap.
The second problem encountered with submersible sensors and pumps is how to support the weight of those devices together with the service cable. If the sensor or pump is relatively light and the well relatively shallow then the service cable itself may be strong enough to support device. If the weight of the submersible unit is sufficiently high, however, the service cable may become dislodged from the harness even though the load is on the cable is well below its tensile strength. Even heavier units will require some load bearing structure in addition to the cable itself for support.
Another problem encountered with the use of submersible sensors and pumps is determining the depth to which the device has been lowered in the well. One solution to the problem has been to place regularly spaced markings or indicators on the service cable from which the depth of the unit can be calculated. A simple approach to the problem is to print such markings on the exterior surface of the cable jacket but it has been found to be difficult to print on curved jacket surfaces and to prevent the markings from being rubbed off during usage. Another approach has been to impress the markings in the jacket by heat stamping and then to fill the impressions with epoxy or another filler to make them more visible. The resulting markings are durable but the process is relatively expensive. Another known method of cable marking involves the application of spaced circular bands containing distance markings to the cable. Again, the resulting markings are relatively durable but the process is costly.
Accordingly, it is an object of this invention to provide for an improved service cable and cable harness for submersible sensors and pumps which will minimize the possibility of leakage into the device.
Another object of this invention is to provide for an improved cable and harness which can support heavier pumps and sensors without the inclusion of reinforcing structure in the cable.
Another object of this invention is to provide for a reinforced cable and harness which can be used with heavier sensors, pumps and extended length cable.
Yet another object of this invention is to provide for a service cable having durable and easily visible markings from which the depth of a sensor or a pump in a well can be computed and an inexpensive method for applying such markings to the cable.